This invention relates generally to optical communications, and more particularly to high power semiconductor lasers and amplifiers.
Optical fiber communication systems preferably provide low loss and high information carrying capacity. In a typical optical fiber communication system, fiber amplifiers are used to maintain the amplitude of the signal and the integrity of the data it carries between a source and destination. However, as optical fiber systems increase in size and complexity, so does the need for higher output power fiber amplifiers and lasers.
The output power of semiconductor pump lasers and integrated laser amplifiers comprising a semiconductor laser optically coupled to a power amplifier is generally limited either by thermal effects or by beam instabilities. For example, the overall output power may be increased by the area of the device that is pumped. However, there are limitations on the size of the area that may be efficiently pumped. For example, if the width of the device is increased, the optical waveguide may support multiple spatial modes, potentially decreasing the stability of the beam. Further, if the length is increased, the output power may saturate when the internal optical losses become large compared to the mirror losses. Similarly, the operating current density and therefore the output power of a laser is often limited to avoid excessive device heating.
Recently, cladding pumped fiber lasers have been utilized to overcome the deficiencies of semiconductor pump lasers. Cladding pumped fiber lasers (i.e., the combination of a light source and a cladding pumped fiber) are advantageous in that they allow the coupling and magnification of light from high-power diode-laser arrays into a single mode fiber. However, cladding pumped lasers are often long in length and include non-circular inner cladding designs to more effectively couple the output of the laser diode into the cladding. Such designs are difficult to fabricate and to align with and splice to conventional transmission fiber.
Therefore, while good results have been obtained from cladding pumped fiber lasers, it would be advantageous to provide a high power semiconductor pump laser that can be readily coupled into a single mode fiber, wherein the laser has a reduced system size and cost.
In one aspect of the present invention, a monolithic, high power, single mode electro-optic device includes an electrically pumped device with a pn junction and an optically pumped device evanescently coupled to the electrically pumped device. In operation the electrically pumped device is driven by an external source into a high energy state to emit photons at a first wavelength. The optically pumped device is at a low energy state so as to absorb the emitted photons and re-radiated light at a second wavelength.